In observation of the inner wall of a gastrointestine using an endoscope, a procedure in which the observation is made easier by sprinkling a colorant has been adopted. The colorant which is widely used today is aqueous indigo carmine solution.
In operations has been used a procedure in which a resection area is clarified by marking a site to be resected with a colorant. For example, JP 10-194998 A (patent document 1) discloses a thickener and a living body marking preparation for operations which contains an intermediate color or cool color colorant applicable to the living body. This document reports that injecting the living body marking preparation to a site to be resected with a syringe allow the resection area to become clear during a surgical operation.
It, however, is not always possible to make observation easily when it is difficult to identify a lesion in the case of early cancer or the like. Moreover, it was not easy in operations to determine the margin line between a lesion and a normal mucosa or to properly resect only a lesion. Therefore, a technique by which a lesion can be observed clearly in an endoscopic observation has been awaited.    Patent document 1: JP 10-194998 A